The present invention relates to an improved liquid fuel injector for burners of gas turbines.
As is known, a gas turbine is a machine consisting of a compressor and a turbine with one or more stages, in which these components are interconnected by a rotating shaft and in which a combustion chamber is provided between the compressor and the turbine.
Air from the external environment is supplied to the compressor where it is pressurized.
The pressurized air passes through a series of premixing chambers, each terminating in a nozzle or converging portion, and an injector supplies fuel to each of these chambers, this fuel being mixed with the air to form a fuel-air mix for combustion.
The fuel required for the combustion, which is designed to cause an increase in temperature and enthalpy of the gas, is introduced into the combustion chamber by means of one or more burners, supplied from a pressurized network.
A parallel fuel supply system, for generating pilot flames in the proximity of the outlet of the burner, is also generally provided, generally where gas fuel is used, in order to improve the stability characteristics of the flame.
The gas at high temperature and high pressure then passes through suitable ducts to reach the various stages of the turbine, which converts the enthalpy of the gas into mechanical energy which is available to a user.
Known burner units have a complex structure, within which there is an injector, contained within a converging casing.
The injector, which is obviously connected to a liquid fuel supply line running from a remote reservoir, generally has a body with a cylindrical portion and a pointed terminal portion.
The known type of liquid fuel injector for burners in gas turbines has a channel for the passage of the fuel and has channels for the admission of pressurized air from the turbine compressor.
Both the fuel channel and the pressurized air channel terminate in suitable outlet holes, where the air leaving the injector is used to vaporize the fuel to improve the combustion characteristics.
It is well known that the primary considerations in the design of combustion chambers for gas turbines are the flame stability and the control of excess air, the aim being to establish ideal conditions for the combustion.
A second factor which influences the design of combustion chambers of gas turbines is the tendency to make the combustion take place as close as possible to the dome of the combustion chamber.
Other problems which are particularly significant in the technical field of burners include the necessity of achieving optimal atomization of the liquid fuel and suitable mixing according to the different characteristics of the fuels used.
Finally, it is desirable to achieve optimal conditions of turbulence of the fluids concerned in the premixing area, and to reduce the emission of combustion byproducts, particularly pollutants such as nitrogen oxides.
The object of the present invention is therefore to improve the aforementioned liquid fuel injector for burners of gas turbines in such a way that the emission of pollutants is minimized, but with consideration of other requirements for satisfactory combustion such as those mentioned immediately below.
Another object of the present invention must therefore be to provide a liquid fuel injector for burners of gas turbines which also provides high flame stability.
The objects of the present invention also include the provision of an improved liquid fuel injector for burners of gas turbines which reduces the pressure oscillations in the combustion chamber.
Yet another object of the present invention is to provide an improved liquid fuel injector for burners of gas turbines which produces high combustion efficiency.
An additional object of the present invention is to provide an improved liquid fuel injector for burners of gas turbines which makes it possible to increase the average life of components subject to high temperatures.
Another additional object of the present invention is to provide an improved liquid fuel injector for burners of gas turbines with low emission of pollutants which has an extremely simple and compact structure but which maintains optimal fluid dynamic characteristics.
Finally, another object of the invention is to provide an improved liquid fuel injector for burners of gas turbines which provides excellent reliability of operation of the machine, and which can be made at low cost because it consists of a small number of components: this also facilitates dismantling and maintenance.
These and other objects of the present invention are achieved by making an improved liquid fuel injector for burners of gas turbines as described in Claim 1.
Further characteristics are specified in the subsequent claims.